The 1926 Loomis Special was a redesign by C G Taylor of another plane for barnstormer Jack Loomis (Taylor’s flight instructor). With a steel tube fuselage, Clark-Y wing, and two place cabin under a monoplane wing. Registered N2594 c/n 2, powered by a 120hp Anzani, it crashed in August 1927, and rebuilt as a four place open cockpit with a 135hp Hallett and reregistered N2954.

Engne: 120hp Anzani
Wingspan: 40’0″
Length: 24′

While Northrop was working on the YA-13/XA-16 developments of the Gamma, the company was also testing a scaled-down version for the US Navy under the designation Northrop XFT-1. This was one of two Northrop prototypes which failed to attract production orders, the other being the Type 3-A of 1935. Both were all-metal fighters, the XFT-1 with fixed landing gear being intended for the US Navy. Powered originally by a 466kW Wright XR-1510 radial, it was later re-engined, as the XFT-2, with a 485kW Pratt & Whitney R-1535, but crashed three months later, in July 1936.

The Northrop 3-A was a similar design for the US Army, but differed from the navy aircraft in having retractable landing gear and a modified canopy. Developed alongside these prototypes was the XBT-1, which had semi-retractable landing gear, and this entered production as the BT-1 torpedo-bomber, the first of 54 being delivered in April 1938. The BT-1 had a 615kW Pratt & Whitney R-1535 Twin Wasp Junior radial engine, but one aircraft was modified as the BT-2 to have revised landing gear and a 597kW Wright XR-1820 Cyclone. With other modifications this was to become the Douglas SBD Dauntless as the original Northrop Corporation had by then become the El Segundo Division of Douglas.

Based on the design of the XFT, the Model 3A was developed as a contender in the US Army’s Materiel Division competition for a successor to the P-26 in service with the USAAC. A low-wing all-metal semi-monocoque monoplane with fully-retractable main undercarriage members and an enclosed cockpit, the Model 3A was powered by a Pratt & Whitney SR-1535-6 Twin Wasp Junior 14-cylinder radial engine rated at 700hp for take-off. It had provision for one 7.62mm and one 12.7mm gun in the fuselage. Completed in July 1935, it was briefly tested at Wright Field where it was found to be somewhat unstable and prone to spinning. Returned to the manufacturer for modification, the Model 3A was under test over the Pacific on 30 July, but failed to return, no trace of the aircraft nor its pilot ever being found. The design of the Model 3A was subsequently sold to Chance Vought Aircraft which further developed it as the V-141.

3A
Max take-off weight: 1769 kg / 3900 lb
Wingspan: 10.21 m / 33 ft 6 in
Length: 6.78 m / 22 ft 3 in
Height: 2.77 m / 9 ft 1 in
Wing area: 17.37 sq.m / 186.97 sq ft
Max. speed: 434 km/h / 270 mph

Despite some scepticism concerning the practicability of the monoplane configuration for the shipboard fighter, the US Navy’s BuAer issued a second requirement for such a warplane on 24 January 1933, the first having been issued seven weeks earlier and for which the Boeing Model 273 was designed and built (as the XF7B-1). To meet the later but essentially similar requirement, a contract was let to Northrop for a prototype assigned the designation XFT-1.

A single-seat all-metal cantilever monoplane with split flaps, spatted main undercarriage members and an enclosed cockpit, the XFT-1 was designed by a team led by Ed Heinemann. Powered by a Wright R-1510-26 14-cylinder radial rated at 600hp at sea level and 625hp at 1830m, and carrying two 7.62mm cowl guns, the XFT-1 first flew on 16 January 1934.

The US Navy was critical of its manoeuvrability, its tendency to spin out of certain manoeuvres, its low speed characteristics and its landing speed. During the course of initial tests, an XR-1510-8 engine affording 650hp at 2590m was substituted for the -26, and, in April 1936, the XFT-1 was returned to the manufacturer for more extensive modification. A Pratt & Whitney R-1535-72 Twin Wasp Jnr 14-cylinder radial rated at 700hp for take-off and 650hp at 2285m was installed, this having a long-chord cowling; the vertical tail surfaces were enlarged, and the mainwheel spats were revised.

Redesignated XFT-2, the fighter was now 118kg heavier in empty condition, speed and climb performance were marginally improved, but manoeuvrability and low speed characteristics were worse. It was pronounced unairworthy by the US Navy and crashed on 21 July 1936 while being returned to its manufacturer.

XFT-1
Max take-off weight: 1704 kg / 3757 lb
Empty weight: 1120 kg / 2469 lb
Wingspan: 9.75 m / 31 ft 12 in
Length: 6.43 m / 21 ft 1 in
Height: 2.87 m / 9 ft 5 in
Wing area: 16.44 sq.m / 176.96 sq ft
Max. speed: 378 km/h / 235 mph
Range: 1570 km / 976 miles

While the Gamma was being developed, Northrop was working on a nine-seat transport, which was basically a new fuselage married to Gamma wings. Unfortunately for Northrop, the US 1926 Air Commerce Act was amended to prohibit the use of single-engine aircraft for carrying passengers by night, or over rough terrain where emergency landings could not be made. Consequently, airline use for its intended role was nonexistent in the USA, although three had been sold before the new regulation was announced. Eight others were used as executive transports, and one was bought by Swedish AB Aerotransport, which subsequently acquired a second.

The US Coast Guard operated a Delta under the designation RT-1, as the Secretary of the Treasury’s personal aircraft.

The last Delta was supplied to Canada as a pattern aircraft for assembly in that country by Canadian Vickers, who built 20 of various marks with both wheel and float landing gear. Deltas were flown with various engines, including the 529kW and 548kW Wright SR-1820, 485kW, 492kW and 522kW Pratt & Whitney Hornets.